Method of manufacturing rubber articles



20 conditions.

Patented June 21, 1932 UNITED STATES PATENT OFFICE EARDLEY HAZELL, OF NEW YORK, N. Y., ASSIGNOR TO THE NA'UGATUCK CHEMICAL COM- f PANY, F NAUGATUCK, CONNECTICUT, A CORPORATION OF CONNECTICUT METHOD OF MANUFACTURING RUBBER ARTICLES No Drawing.

0 vide a process for increasing the rate at which rubber may be deposited in a desired shape or condition by (1) dilution (2) the addition of substances increasing its ability to filter off the aqueous portion through the deposit as it builds up in thickness (8) agitation and (4) heating. The rate of deposition may be increased by employing some of the steps above mentioned, but maximum-results may be obtained by using all of them under optimum The stability of the latex c0mposition against coagulation, and the ability of the latex to hold in uniform distribution compounding ingredients for imparting desired characteristics to the finished article and to maintain a constant consistency are also improved by the present invention. These are some of the objects of the invention, others will be manifest to those skilled in the art from the subsequent detailed description.

With the preferred process in mind, but without intention to limit more than is required by the prior art, the invention, briefly stated, consists in diluting the; latex or dispersion to lower its solid content, adding substances thereto which increase its filtertubes, hose (garden or fire), rubberized fabrics or articles, gloves of rubber only or of rubber and fabric, boots and shoes made wholly of rubber or of rubber and fabric, or

comprehensively stated, of any kind of rubber article to which the invention is applicable. In the specification and claims the expression porous form is used to compre- 59 hend any permeable material on which, by

Application filed August 19, 1927. Serial No. 214,205.

whether the surface of the material becomes a part of the finished article or not. For in--' stance, the porous form may be of ungl zed earthenware from which the deposit is ultimately stripped, or it may be composed entirely or superficially of fabric. The shape of the porous form may be anything desired." Obviously the pores of the form should be small enough to prevent the entry, of any appreciable amount of rubber particles.

It has been discovered that the rate of dep osition of rubber and like materials from natural latex may be increased by the addition of metallic oxides and sulphide solutions. For instance, if zinc oxide and sodium polysulphide are incorporated in the following composition Rubber latex (preserved with 1% of ammonia r) .100 parts and containing 37.5 parts rubbe Zinc oxid 3 parts Sodium polysulphide solution (42% of solid sodium polysulphide analyzing 32.5% of sulphur) 0.21.0 cc.. Undecylenic acid (crude emulsion) 1 part the rate of deposit as compared with the Rate of deposit The rate of deposit'is taken as the thickness of rubber formed on a porous vessel immersed in a latex for five minutes and then dried.

As another example, a stabilizing ingredient such as glue may be added to latex before the zinc oxide. With this illustration 1 part of glue is added to latex containing 37% of total solids and preserved with. 0.67%. of ammonia. Zinc oxide is added to the latex in the form of a zinc oxide-glue paste containing 1 of glue to 3 zinc oxide per 100 of rubber. After 2 vdays, from 02-07% of sodium polysulphide solution'may then be introduced. The results obtained with this example are illustrated in the following table:

Ccs. sodium polysulphide Rate of deposit solution per 100 ccs. latex Blank .005 .2 .013 .4 I .016 .7 .032

:sulphur present in the latex as combined sulphur can be substantially entirely accounted for in the zinc sulphide formed in the latex. Inother words combined sulphur determinations on the rubber portion of the latex "show substantially the same percentages before and after treatment, indicating that no vulcanization-could have taken place.

Instead of sodium polysulphide, the sulphides or polysulphides of sodium, potassium, lithium, ammonium, maybe used with various degrees of advantage. The Zinc oxide in the example next preceding may be jreplaced by'zinc hydroxide or by any soluble zinc salt-dissolved in water or in a solution containing ammonium hydroxide in excess.

The increased rate of deposit maybe obtained'by 'adding'sulphidesolutions to vulcanized as well as unvulcanized latex. To illustrate this the following example .is given:

A quantity of latex is concentrated and purified'by the addition of 1 part oi hydrophylic material such'as pectine, Irish moss,

-etc.,- and afterzthe rubber portion has sepa-- ..rated :in asupernatent layer, the serum is removed, and ithQ/ :rubber portion diluted with water to give of solids. SA paste consisting of 3 ,partsof zinc oxide, 3 parts of sulphur, 1 part glue, and 4 parts of water is obtained with ordinary vulcanized latex. The inclusion of sodium polysulphide in the "amounts given in the following table greatly zimprovesitheirateoideposit.

Ccs. sodium polysulphide Rate of deposit solution per 100 ccs. latex Blank .0137 .15 .0165 .3 .024 .45 .038

of water. A similar emulsion is also prepared using l part of anilinein place of the 1 .part of disulphide. .These emulsions are then added to the latex, and vulcanization allowed to :take place. After vulcanization has taken place,.the vulcanized latex is treated with sodium polysulphidesolution. The efiect of this solution upon the rate of deposit of the vulcanized latex .is shown in the following table:

Ccs. sodium polysulphide j-Rate of deposit solution per cos.

of latex Blank .0155

A latex which contains :oxy normal butyl crease .its rate of deposit.

The increasedrate of deposit which is be- .lieved to be imparted by the formation of colloidal metallic sulphides or polysulphides inthe-latex may also be accomplished by the formation of other colloidal precipitates in the samemanner. The improvement may also be .gained by the direct addition of colloidal sulphides, polysulphides or precipitates. Rubber obtained from such vulcanized latex, whichhas been treated with sodium polysulphide, shows an appreciable improvement .in tensile strength and in re- :s1stance to ageing.

.Ithas also been discovered that after rub- .ber latex or similar aqueous dispersions which have beentreated to increase the rate of filterability by the .addition of \chemical substances, the rate ofdeposition of such latex or dispersion may be increased by agi- ,tation, or heating, or both, the latter augmenting the rate of deposition bythe sum of the increments of each'treatment. General- .ly the agitation may be carried on continuously or intermittently and the heat treat- .ment maybe varied iromroom temperature up .to a temperature belowthat causingcoagulation. .As one illustration of this phase of'the invention, a natural-rubber latex, ammonia preserved and containing 30% of .total solids,'may have the property of rapid *filterability imparted to it by the "following treatment: To 100 "parts of rubber in the form of latex are added a small amount of stabilizing agent and about 3 parts of zinc oxide and a solution of sodium polysulphide containing approximately 42% of solid .sodium polysulphide analyzing 32.5% of sulphur, (.9 cos. of this solution, sp. g. 1.33 per 100 cos. of latex). Preferably, although not necessarily, a small amount of a stabilizing agent is added with the polysulphide, say A to parts by weight of sodium oleate or undecylenic acid in the form of a soap or aqueous emulsion or glue or casein or any of the customary protective colloids used in latex. This composition after standing for a short time has the property of rapidly depositing its rubber upon a filtering body, that is, it possesses the property of rapid or easy filterability. This composition when disposed in contact with a filtering medium such as a porous plate or vessel or other filtering medium will give a thickness of deposit of about .030 inches in 5 min. If this same latex composition be stirred either continuously or intermittently at a speed of lineal feet per minute for a total of 45 min., and subsequently deposited the rate of deposit under the same conditions will be increased by 150%. If this same latex be heated to 40 (3., the rate of deposition of the rubber in the latex under the same conditions will be increased by about 50%. If both stirring and heating be applied to the latex composition, the rate of deposit is approximately 200% greater than the unheated latex without these treatments, that is, the total increase is approximately the sum of the increase gained by the separate treatments.

The beneficial effect caused by the foregoing treatment of latex may also be secured with latex containing compounding ingredients. For example, a latex suitably compounded for the manufacture of articles may be treated with say zinc oxide and sodium polysulphide as above described, the zinc oxide and the sodium polysulphide being added in about the same proportions with reference to the rubber in the latex composition as herein described. A composition containing Rubber as 39% latex 100 parts Zinc oxide 5 parts Glue 3 parts Sulphur 1.60 parts Whiting 10 parts O 3 parts 10.0 parts 0.15 parts 0.5 parts 2.25 parts Accelerator 0.15 parts Water 21.0 parts Sodium polysulphide 0.95 ccs. per 100 cos. of latex (about .5 parts by weight) will yield a deposit of rubber (after drying) of about .07 inches in 45 min., the latex being heated to 23 C.

increase the rate of filterability by the addi tion of substances other than metallic oxides and polysulphides. Generally stated, these other substances embrace gel-forming colloids, bu'fier solutions which influence the de-" 'gree of aggregation of the particles of rubber by control of their hydrogen ion concentrasubstances so generally referred, to have been disclosed in prior patent to Hopkinson and Gibbons No. 1,632,759 granted June 14, 1927 and reference is made thereto for a full understanding of the scope of this phase of the invention. 4 v It has furtherbeen discovered that by diluting the latex or dispersion the rate of deposition may also be increased. The extent of dilution may be varied Within wide-limits but the greatest advantagehas been obtained I with'a latex composition containing between 8 and 24% solids, the optimum dilution being around 14% solids. Latex diluted within the range above mentioned and to which are added substances such as those above mentioned increasing its rate of filterability through a porous form, upon agitation or heating, or both agitation and heating, has been found to deposit more rapidly or yield a layer of rubber of greater'thickness in a given time than the same latex composition which has not been diluted. As an illustration, the above mentioned latex composition may be employed, using various concentrations of latex and adding foreaoh 100 cos. of

latex 0.9 cos. of an aqueous solution of sodium polysulphide containing 42.5% of polysulphide. The beneficial efi'ectupon the rate of filterability may be seen in the following table:

Concentration Thickness of deposit (dry) 88.8 .070 inches concentration of latex is 14%, where the increased rate of deposit due to dilution of the latex is about 350%. I If each of the compositions represented by the above range of dilutions be agitated just after preparation :for a time, it will be observed that the thickness of deposit will be further increased by -175%. If each 7 of therespective compositions be heated after preparation to say 35 0., each willshow an increased rate of deposit of about"50%. When both agitation and heating are employed, the increase in rate of deposit is the sum of: the increments gained by the separate treatments iofiagitation and heating. XIII {other words the increase :due ;to agitation rand heatingxwill :be 17.5'722570 or :roughly 'iabo-ut 200%. :Selecting a.l-atexof19+20% solid:contentzandiagitating justafter prep- 4 aarationforl hr. at allinealsspeedof'r'O :feet :per imin., a deposit roof. .375 inches thickness emayibeiobtainediinA5amin. Ifithe. same latex :enmposition befheated to 35 :10. after the zagitation,:thezthicknessof deposit upon dryzing will be w0.5 inchesfin the same length :of :time (45:;min.)

*In theiahove t8.bl8'.l3ll8.thlCkI1eSS'Of deposit iisithat obtained by filtering-the latex :com-

1 position :on ;abo.dy :composed of paper pulp and ;celite,1under :a pressure corresponding :to 130-170 :cm. .nfJmercury, the-filtering temiperatures'being approximately 222tgC.

It has still further been discoveredthat the increased rate *ofadepositobtained by dilut- -.ing :the latex :is ;augmented *when the ;sub- EStflIICQSLlIlCI'GfiSlIlgI its rate of; filterabilit'y. are :-employed in :certain definite proportions rel- -ativezto .thevolumeQftheElatex, and thatiagittating and/or :heating such latex -.comp.osi-, :tions containing :the ;optimum' quantities of the ,Sll'bStEl-IICGS yield deposits 'ofmaximum "thickness. Hence, theiinvention in :its pre- .ferred-em'bodirnentcontemplates' dilution, the

addition 'Within :certain limits of idefin'ite quantrtiesrofsubstances'increasing the rate of filterability, :agitation, :and heating. .Furthermore, in this preferred procedure there is" thegleast difiicultyfrom air bubbles forming; inrthe deposit.

Fromlatex compositions similar toxthose above mentioned containing varying amounts 10f *total solids "and "also containing varying amounts of polysulphide'solution-per 100 .cc. f of .1latex,"the:followin g .table of observations as to the raterof. deposition was made Weight of deposit in "grams per 92.5-0711 m-mim 005. of 42.5% polysulphide latexcomposition employed is vulcanized oradded to the latex should 'bemade for the solution .per .100 cos.. of latex Concentration 0t Iatex solids .8 cos. .9 cos. 1.0 ccs.

Grams Grams 8 1O 44 32. 5 1S 20 12 .15 12 v12 The same latex compositions ,uponagita- ,tionafter preparation yielded a depositper w-unit-area in the same length of time approxiimately.l50,% greater in thickness'than when knot agitated. :Similarly on heating after preparation, an increased weight of deposit in the: same length 'of time amountedto about 50% of that obtained at room'temperature. If both agitation and heating be utilized :the total increase :in :amount of rubber deposited :in unit time will :be in .the neighbor- :hood of.200.% fforeachaconcentration. From this .it1is apparentthat the increase gained by selecting themost favorable amount of polysulphide zcarries :through the subsequent agitationandheating treatments. .Theigreat .est depositjs obtainediwithalatex contain- ;.ing145% .of'solids and aboutz0.9 ccs. of polysulphide solution'per 1'00 ccs.*ofj.latex. With latex containing ;14l% solids the most favorable .quantity of polysulphidewhich should beadded ranges between/7 5 and 1.1% of a 42%1solution'of Na S aq.,.these percentages being byrvolume on anormal ammonia preserved latex containing about 5% of .zinc oxide :on theirubber. When, however, the

'80 heavily compounded, for is made up with a creamed latex, a'wlderrrange of percentage 301" polysulphidemay be used, for example 0.1 cc.2.0 'cc. of polysulphide solution per 100-ccs. oflatex. A 42% solution of sodium polysuphide is :a convenient concentration, but other concentrations may be used, it being understood that corresponding corrections' on the percentage of .polysulphide W particular concentration of polysulphide solution. The solution containing approxi- .mately 42% of'polysulphide isquite convenient tozhandle inpractice andin manyre spects is preferable to .moredilute solutionsfi While'the inventionxhasthus far referred -.=mainly toincreasing the rate ofifiltration or the weight of depositjofrubberupon afiltering body the'treatmentszalso have another beneficial eflectythat ofinfiuencing the con-" sistency of the latex composition. Latices having arapidrate of depos1t1on or being capable of depositing their rubber by filtrationywill show a high consistency, that-is, will be'quiteithick, possessinglow mobility :and/or fluidity. This consistency frequent- 1y shows a tendency to vary, the .result of which is thatxthe rate of filtration'will show a variation for "the :same composition upon standing. It :has been discovered that the agitation :and heat treatment herein doiscribed have amarked effect .upon theconisistency of the filterable :latex compositions.

of latex to 8-24% solids also hasa favorable effect uponthe reduction of the consistency of the composition. Referring more particu larly: to the manufacture of articles by filtra- H tion .methods, the reduction in consistency 1 move bubbles from the composition and thus to prevent imperfections during the manufacture of articles.

The invention may be applied to the manufacture of any article to which it is adapted whether made entirely of rubber or partly of rubber and fabric or other material. It may be used in conjunction with electro-deposition processes as well as in simple deposition on a porous form, inasmuch as the increased rate of deposition which may be obtained by the employment of this invention augments the rate of deposit obtained by the passage of an electric current. It of course also may be used for filtration under elevated or reduced pressure. I

The invention is primarily concerned with increasing the rate of deposition of rubber or similar materials from their latices as obtained from the plantations but is applicable to artificially prepared latices sufficient ly imitating natural latex to be susceptible of the processing of the present invention with advantage. The term latexinthe specifi cation and claims comprehends natural latex and such artificially preparedlatices, and in cludes Hevea latex as well as the species other than Hevea. All substances which increase the rate of filterability of the latex have been i found to cause it to more rapidly deposit on a porous form when diluted, agitated,. and/0r j heated, and particularly when the substances added to increase the rate of filterability have been incorporated in optimum proportions. It is to be understood, however, that Having thus described my invention,.what I claim and desire to protect by Letters Patent is: I

1. A process for manufacturing rubber ar ticles from latex which comprises treating the latex with material which increases its filterability, agitating the latex prior to the deposition thereof to further increase its filterability, retaining the said material in the latex, and depositing rubber from the thus. treated latex on a porous form.

2. A method of increasing the rate of deposition of rubber from latex which comprises treating the latex with material which increases its filterability, agitating the thus treated latex prior to the deposition of'rubber therefrom and while retaining the said ma terial in the latex.

3. A process for manufacturing articles from latex which comprises treating the latex with a zinc compound and a polysulphide, agitating the latex, and depositing rubber from the thus treated latex.

4. A method of increasing'the filterability of latex which comprises treating the latex with a colloidal metallic sulphide and agitating the thus treated latex.

.51. A process for manufacturing rubber articles from latexwhich comprises treating the latex with material which increases its filterability, agitating the latex while retaining the said material in the latex, and depositing rubber from the thus treated latex.

6. A process for manufacturing rubber articles from latex which comprises treating the latex with a zinc compound and a polysulphide, heating without an accompanying vulcanization of the latex, and depositing rubber from the thus treated latex on a porous form.

7 A method of increasing the filterability of latex which comprises treating the latex with a colloidal sulphide, and heating the thus treated latex without an accompanying vul canization.

8. A method of increasing the filterability of vulcanized latex which comprises treating the latex with colloidal zinc sulphide and heating the thus treated latex. I 9. A process for manufacturing rubber articles from latex which comprisestreating the I latex with material which increases its filterability, agitating and heating the latex prior to deposition of rubber therefromwhile retaining the said material in the latex, and depositing rubber from the thus treated latex.

10. A process for manufacturing rubber articles from latex which comprises diluting and treating unvulcanized latex, without an accompanying vulcanization, with material which increases its filterability, and depositing rubber from the thus treated unvulcanized latex.

11. A process for manufacturing rubber articles from latex which comprises diluting the latex, treating the latex with material which increases its filterability, agitating the latex while retaining the said material in the latex, and depositing rubber from the thus treated latex.

12. A process for manufacturing, rubber articles from latex which comprises diluting and; treating unvulcanized latex with mate rial whichincreases its filterability, heating thelatex: without an accompanying vulcanization, and depositing rubber from the thus.

.treated latex.

-l3.'.A process for'manufacturing rubber articles :fromlatex which comprises diluting the. latex, treating the latex with material which increases its filterability, agitatingthe.

Q-.latexIwhileretainingthe said material in the latex, heating the latex, and depositingrub= berfrom the thus treated latex.

14; A method of increasing the. rate of deposition of rubber from latex whichcom- 5 prises diluting unvulcanized latex .to a solid 'content between 8 and 24% and treatingthe unvulcanized latex, gin theabsence of an accompanyin'g. vulcanization, with material which increasesits filterability.

of latex which comprises dilutingthe latex to asolid content between 8 and 24%, treating the latex with material which increases its filterability, and agitating the latex while.

retaining. the said material in the latex. V 16. A method ofincreasing the rate of deposition of rubber from latex which comprises diluting unv'ulcanized latex to a solid content of between 8 and 24%, treating the unvulcan- Q ized latex with material which increases its filterability, and heating the latex without an accompanying vulcanization.-

. 17. A methodof increasing the filterability of latex which comprises diluting-the latexto a-solid content between'8 and 2 l%,.treating.

the'latex with material which increases its filterability, heating the latex andxagitating. the latex while retaining the said. material in the latexi Q- 18. A, process for-manufacturing rubber articles fromzlatex which comprises treating:

the latex with a colloidalsulphide without an accompanying vulcanization of the latex, and

depositing rubber from the thus treated 4 latex.

19.-A- process for manufacturing rubber articles from latex, which. comprises -treatingv unV-ulcanized latex, without an accompanying. vulcanization, with a metallic compound and a=-polysulphide to form therewith-acolloidal sulphide, and'depositing rubber from the thus treated latex on i a porous form in the shape desired,

.20. A. process for manufacturing. rubber artic-les-from latex which comprises treating. unvulcanized latex without an accompanying vulcanization, with a compound of bivalent metal: an'd a solution of a polysulphide which together reactto increase the'filterability of 'lat6X\find* depositing rubber from the thus treated late-x .on a-porous'. form in theshape: desired by. withdrawing; aqueous matter: through the form and removing said:matter.

.21. I A process-tor manufacturingrubber articles; from; latex. whichcomprises-.- treating,

15. A method of increasing the filterabilityunvulcanizedlatexiwithoutianaccompanying vulcanization with: a zinc; compound and a solution of: sodiumpolysulphide to. form: a colloidal zinc" su1phide,and depositing rubberfrom the thus treatedlatexon a porous form in the shape desired.

22. A method of increasingxthe filterability of unvulcanized-latex whichcomprises treats ingthe.unvulcanizedlatex with colloidal sulphide in the absence ofanaccompanyingvulcanization of the latex.

23. Amethodof increasing thefilterability of latexwhich comprises :treating latex with colloidal zinc sulphide inthe absence of an accompanying;vulcanization of the latex.

24. Amethod ofincreasingthe filterability of vulcanized. latex which? comprises treating the vulcanized'latexwith colloidal sulphide.

25; A method of increasingthefilterabilityof latex which comprises: treating latex with a metallic compound and a solution of olysulphide in the absence of anaccompanying vulcanization of the latex.

26. A method of increasing the filterability of latex whichcomprises treating latex with a zinc compound and a solution of sodium polysulphide in the absenceofan accompanying vulcanization. of the latex.

of. latex which comprises diluting. the latex to. a solid contentbetween 8. and24 -%,-and" treating the latex, intheabsenceof an accompanying vulcanization, with. a metallic compound anda vpolysulphide insolution to form therewith. a colloidal sulphide.-

28. Amethod of increasing ;the filterability' a polys ulphidein solution'toform therewitha colloidal sulphide, and heating theilatex without an accompanying vulcanization;

'30: A method of increasing the filterability' of latex which comprises diluting the latex to a solid content'between-8' and' 24%, treating the latex with ametallic'compound and' a polysulphide insolutionl to form' therewith a-colloidalsulphide; heatingithe: latex and agitating; the latex while: retaining the said;

substances in the latex.

31. A process for manufacturing. rubber articles. directly, from latex .which: consists :in diluting, the; latex? to: a: solid 5 content between 8 and 24%, adding to the latex a metallic I compound-and :the equivalentfof. between .7 5

and 11% by: volume offer-42%. solution ofia polysulphidewhich-togetherreactito increase 27. A method of increasingith'e filterability the filterability of latex and depositing rubber from the thus treated latex on a porous form in the shape desired by withdrawing aqueous matter through the form and removing said matter.

32. A process for manufacturing rubber articles directly from latex which consists in diluting the latex to a solid content between 8 and 24%, adding to the latex a metallic compound and the equivalent of between .75 and 1.1% by volume of a 12% solution of a polysulphide to form therewith a colloidal sulphide, agitating the latex, and depositing rubber from the thus treated latex on a porous form in the shape desired by withdrawing aqueous matter through the form and removing said matter.

33. A process for manufacturing rubber articles directly from latex which consists in diluting the latex to a solid content between 8 and 24%, adding to the latex a metallic compound and the equivalent of between .75 and 1.1% by volume of a 42% solution of a polysulphide to form therewith a colloidal sulphide, heating the latex, and depositing rubber from the thus treated latex on a porous form in the shape desired by withdrawing aqueous matter through the form and removing said matter.

34. A process for manufacturing rubber articles directly from latex which consists in diluting the latex to a solid content between 8 and 24%, adding to the latex a zinc compound and between .75 and 1.1% by volume of a 42% solution of an alkali polysulphide, agitating and heating the latex, and depositing rubber from the thus treated latex on a porous form in the shape desired by withdrawing aqueous matter through the form and removing said matter.

35. A process for manufacturing rubber articles from vulcanized latex which comprises treating the vulcanized latex with colloidal zinc sulphide, and depositing rubber from the thus treated latexon a porous form in the shape desired.

36. A process for manufacturing articles from vulcanized latex which comprises add ing material which increases the filterability of the vulcanized latex, diluting the latex, and depositing rubber from the thus treated latex.

37. A method of increasing the filterability of vulcanized latex which comprises diluting and adding colloidal zinc sulphide to the vulcanized latex.

38. A process for manufacturing articles from vulcanized latex which comprises adding material which increases the filterability of the vulcanized latex, diluting and heating the latex, and depositing rubber from the thus treated latex.

39. A method of increasing the filterability of vulcanized latex which comprises diluting,

heating and adding colloidal sulphide to the vulcanized latex.

Signed at New York, county and State of New York, this 18 day of August, 1927.

EARDLEY HAZELL. 

